Camera systems used in vehicles generally have a camera housing, a circuit substrate including additional electronic components, and an imager module that is contacted by the circuit substrate. The imager module itself generally includes an image sensor, a sensor carrier for mounting the image sensor, and an objective lens. The objective lens is mounted to the sensor carrier via a lens holder, for example. Thus, the image sensor and the objective lens define an optical axis. The image sensor can be mounted on the sensor carrier directly or via a chip carrier and is contacted via the sensor carrier, for example via circuit-board conductors of the sensor carrier that lead to the circuit substrate.
An imager module of this kind is first mounted as a unit and focused by adjusting the objective lens along the optical axis relative to the image sensor. The prefabricated imager module can then be subsequently contacted by the circuit substrate and accommodated in the camera housing.
The objective lens can first be laterally positioned via a clearance fit relative to the tube of the lens holder. The objective lens is axially positioned relative to the lens holder and is, therefore, focused, for example, by frictional action or through the use of a thread pitch. The rear lens space, i.e., the optical space between the rear lens of the objective lens and the image sensor, is sealed against the gap of the clearance fit, for example by a sealing ring or O-ring seal.
Generally, thread formations are relatively costly, however. Furthermore, a thread must always be dimensioned with clearance in order to prevent a seizing/blocking thereof during focusing. The clearance, in turn, can lead to a misalignment of the objective lens in a subsequent processing step and thus to a loss of focus. The thread formation along with the longitudinal position also define the angular position of the lens system, so that a suitable azimuth orientation, i.e., angular position relative to the optical axis or axis of symmetry can be selected without supplementing the longitudinal positioning. Screw-fastening processes are also more time-consuming than purely linear movements.
The disadvantage of longitudinal adjustments that involve frictional action is that particles can be produced by the relative displacement at the contact surfaces, i.e., in response to the friction of the mating surfaces and of the seal upon assembly of the objective lens. When working with image sensors that are unpackaged and are, therefore, freely oriented by the sensitive surface thereof toward the objective lens, the thus produced particles generally have a damaging, harmful effect, since, starting at a certain size within the range of the pixel size of the image sensor, for example a few micrometers, the particles can lead to unwanted cluster defects on the image sensor.
German Patent Application DE 10 2006 000 641 A1 describes mounting an objective lens in a lens holder, a clamping ring being set externally around the lens holder and being tensioned by reducing the diameter thereof However, such significant tensioning forces can lead to permanent deformations of the lens holder and thus to a defocussing. Furthermore, chipping can occur upon introduction of the lens system into the lens holder, and the chipped material can fall on the image sensor and thereby adversely affect image quality.
German Patent document DE 69 628 120 T2 describes anchoring haptics by fusion to an optical element. A microscope design provides for another objective lens to be additionally mounted to act as a collimator upstream of a microscope objective lens. A brass sleeve is used to mount the objective lens in a narrower section near the microscope objective lens. A crimping sleeve engages displaceably with the microscope body and has the purpose of supporting a laser delivery system that uses optical fiber cable. In this case, cylindrical sections make up the crimping sleeve.